IMSLP:Special:RateFile/MainText

Enter a whole number between 1 (worst quality) and 10 (best quality) inclusive.

Also, do not rate a file if you cannot open it; if you use IE this is usually a problem with your browser, and not IMSLP. Get a better browser (Chrome, Firefox or Opera), or clear your cache and try again. More information on this can be found here. If the problem persists, leave a note on the talk page of this work page. Do not rate a file until you are able to open it.